79 K10 Back Fire

[HotRodPC]

Vacuum test, compression test, pinpoint the cylinder, then I would see if you can adjust the exhaust valve for that cylinder and eliminate it.

Yep, do this and lets hope you find something and that it's not valvetrain related.
I know what you mean as far as ideling and revving it up and it's faint. That's because the motor is not under any strain. Put the motor under strain, like in Drive or Reverse, the backfire would become more profound. I'll take a guess, if you put it in D with foot on the brake as if to do a power brake burnout, the backfire is going to be very profound.
But, lets get those Vac and Compression tests done and see the results. Remember a good compression test is all plugs out and a good charged battery to crank the motor over real good.

 

[Kapdin]

Im back with an update, I got the take drained and filled installed new fuel pump and line and put an inline fuel filter and replaced the carb one. I removed the propaine gas lines and disconnected it and installed a Napa crome air cleaner cus i didn't have a base to put my air cleaner on after the lpg settup was gone off the carb. That air cleaner base tho dosn't seem to sit right on the carb like it drops to low on to all my hoeses on the motor so i dunno if its a perfect seal on the carb. But anyways for the test drive, its alot better than it was, less back fire going into gear and now i can be easy on the throttle and no back fire but when i give her the onion its still there. I took it for a 2 mile cruse and as long as i never punched it smooth runnin. Im priceing out all new vacume lines as wee speek but since i forgot to messure last night any one know wat size i should get? 3/16", 1/4", 5/16", 3/8"??? ima replace all vacum emmision hoeses and rewrought them.

 

[89Suburban]

I'd measure mine for if you like, but it's 10 years difference.

About that air cleaner, you already test drove it so I guess you made sure it isn't contacting any of the control linkages. Usually they come with the right spacers and adapters you can adjust to fit, but it's been years since I messed with stuff like that.

 

[Kapdin]

Well i can order them from work here for a good price but the order wont go out till monday anyways so no biggie. i did find these too which should help if my eyes don't go buggy from stairing at all them fuggin hoeses.

 

[89Suburban]

Cool. You don't have the original labels or are they it?

 

[Kapdin]

The origanal should be under the hood correct? I cant find them so i hooked up with my best friend "google".

 

[89Suburban]

Yeah usually on the radiator support or fan shroud.

 

[Kapdin]

I see they make air cleaner spacers, ima pick one up after work here any idea wat size my carb is?

 

[89Suburban]

I see they make air cleaner spacers, ima pick one up after work here any idea wat size my carb is?

What kind of carb?

 

[Kapdin]

Stock 4bbl thinks its a "rochester"?

 

[89Suburban]

Quick search on Rock Auto says 5 1/32" diameter for Quadrajet.

 

[Kapdin]

So wat should i do with any hoes that should go to the air cleaner now that i have this aftermarket cleaner? can i just plug them? Also the valve cover hose? just put a filter on it?

 

[89Suburban]

So wat should i do with any hoes that should go to the air cleaner now that i have this aftermarket cleaner? can i just plug them? Also the valve cover hose? just put a filter on it?

The vac hose going to the blend door on the snorkel can be plugged, and yah, the breather hose can be pulled and stick in a filter. I wouldn't remove any more than that looking at those diagrams.

 

[Jims86]

Autozone.com should also have your Vac diagram in the repair manual section online.
just input the trucks info as if you were looking for a specific part, then click on the repair info, and a sub list should come up. Emissions diagrams, or just "diagramsAlso, check your timing with the vac line unplugged, and in drive....set it at 4* BTDC as a good starting point, then bump it back up when you have fixed the problem.

 

[Kapdin]

Ok so i just replaced all my vac and emission hoeses and it looks good and they are all tight. I also got a gasket on my carb to air cleaner and sits good and tight. ... still back fire. Is there a chanse that its just running rly rich? and its unburnt fuel? and if so can i adjust it ez? I know nother about these carbs.